QUIC's Connection ID Mechanism vulnerable to Memory Exhaustion Attack

quic-go is an implementation of the QUIC protocol in Go. Prior to version 0.42.0, an attacker can cause its peer to run out of memory sending a large number of `NEW_CONNECTION_ID` frames that retire old connection IDs. The receiver is supposed to respond to each retirement frame with a `RETIRE_CONNECTION_ID` frame. The attacker can prevent the receiver from sending out (the vast majority of) these `RETIRE_CONNECTION_ID` frames by collapsing the peers congestion window (by selectively acknowledging received packets) and by manipulating the peer's RTT estimate. Version 0.42.0 contains a patch for the issue. No known workarounds are available.